<!DOCTYPE html>
<html lang="zh-CN">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
</head>
<body>
    <p><strong>这是一段strong的文本</strong></p>
    <p><em>这是一段em的文本</em></p>
    <p>a<sup>2</sup>+b<sup>2</sup>=c<sup>2</sup></p>
    <p>H<sub>2</sub>O</p>
    <p>促销：原价<del>300</del>，现价<ins>100</ins></p>
</body>
</html>